ngspice/examples/various/FFT_tests.cir

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FFT_tests http://www.idea2ic.com/
.control
set units=degrees
let a = vector(16)
*plot a vs a
set pensize = 2
*=========Need_a_complex_input====================
let ac = a+j(0)
print a ac
*plot fft(a) vs a
*plot real(fft(ac)) imag(fft(ac)) vs a
* fft(a) fft(ac)
*=========DC_Works====================
let b = unitvec(16)
let bc = b+j(0)
*plot fft(b) vs a title DC_WORKS
*print fft(b) fft(bc)
*=========DC_Plus_cos_Remove_AC====================
let numb = length(b)
print numb
let indx = 0
repeat $&numb
let ac[indx]= cos(indx*360/8)+1 +j(0)
let indx = indx +1
end
let fftac=fft(ac)
plot real(fftac) imag(fftac) vs a title DC_Plus_COS
let fftac[2]=(0,0)
let fftac[14]=(0,0)
let ifftac = ifft(fftac)
plot ifftac ac vs a title COS_REMOVED
*=========DC_Plus_cos_Remove_DC====================
let indx = 0
repeat $&numb
let ac[indx]= cos(indx*360/8)+1 +j(0)
let indx = indx +1
end
let fftac=fft(ac)
let fftac[0]=(0,0)
let ifftac = ifft(fftac)
plot ifftac ac vs a title COS_With_DC_REMOVED
*=========DC_Plus_sin_Remove_AC====================
let indx = 0
repeat $&numb
let ac[indx]= sin(indx*360/8)+1 +j(0)
let indx = indx +1
end
let fftac=fft(ac)
plot real(fftac) imag(fftac) vs a title DC_Plus_SIN
let fftac[2]=(0,0)
let fftac[14]=(0,0)
let ifftac = ifft(fftac)
plot ifft(fftac) ac vs a title SIN_REMOVED
*=========DC_Plus_sin_Remove_DC====================
let indx = 0
repeat $&numb
let ac[indx]= sin(indx*360/8)+1 +j(0)
let indx = indx +1
end
let fftac=fft(ac)
let fftac[0]=(0,0)
let ifftac = ifft(fftac)
plot ifft(fftac) ac vs a title SIN_With_DC_REMOVED
*=========DC_Plus_cos_Nyqusit_Remove_DC====================
let indx = 0
repeat $&numb
let ac[indx]= cos(indx*360/2)+1 +j(0)
let indx = indx +1
end
plot ac vs a title Nyq_COS
let fftac=fft(ac)
plot real(fftac) imag(fftac) vs a title Nyq_FREQ_COS
let fftac[0]=(0,0)
let ifftac = ifft(fftac)
plot ifft(fftac) ac vs a title COS_With_DC_REMOVED
*=========DC_Plus_sin_Nyqusit_Remove_DC====================
let indx = 0
repeat $&numb
let ac[indx]= sin(indx*360/2)+1 +j(0)
let indx = indx +1
end
plot ac vs a title Nyq_SIN
let fftac=fft(ac)
plot real(fftac) imag(fftac) vs a title Nyq_FREQ_SIN
let fftac[0]=(0,0)
let ifftac = ifft(fftac)
plot ifft(fftac) ac vs a title COS_With_DC_REMOVED
*=========DC_Plus_COS_Remove_One_BIN====================
let indx = 0
repeat $&numb
let ac[indx]= cos(indx*360/8)+1 +j(0)
let indx = indx +1
end
let fftac=fft(ac)
let fftac[2]=(0,0)
plot real(fftac) imag(fftac) vs a title DC_Plus_Cos
let ifftac = ifft(fftac)
plot ifft(fftac) ac vs a title ONE_BIN_REMOVED
plot real(ifft(fftac)) imag(ifft(fftac)) vs a title ONE_BIN_REMOVED
.endc
.end